Showing papers by "University of California, Santa Cruz published in 1977"

History of the Mediterranean salinity crisis

Abstract: A history of geodynamic evolution of the Mediterranean leading to the salinity crisis is outlined, based on the ‘desiccated deep-basin model’. An accurate portrayal of the crisis is presented, based on data from new drilling and studies of on-land geology.

The dynamics of density dependent population models.

Abstract: The dynamics of density-dependent population models can be extraordinarily complex as numerous authors have displayed in numerical simulations. Here we commence a theoretical analysis of the mathematical mechanisms underlying this complexity from the viewpoint of modern dynamical systems theory. After discussing the chaotic behavior of one-dimensional difference equations we proceed to illustrate the general theory on a density-dependent Leslie model with two age classes. The pattern of bofurcations away from the equilibrium point is investigated and the existence of a "strange attractor" is demonstrated--i.e. an attracting limit set which is neither an equilibrium nor a limit cycle. Near the strange attractor the system exhibits essentially random behavior. An approach to the statical analysis of the dynamics in the chaotic regime is suggested. We then generalize our conclusions to higher dimensions and continuous models (e.g. the nonlinear von Foerster equation).

Conjugated polyene fatty acids on fluorescent probes: spectroscopic characterization.

Abstract: This paper is the first in a series which extends introductory studies of parinaric acid and its phospholipid derivatives as membrane probes (Sklar, L.A., Hudson, B., and Simoni, R.D. (1975), Proc. Natl. Acad. Sci. after U.S.A. 72, 1649; (1976), J. Supramol. Struct. 4, 449). Parinaric acid has a conjugated tetraene chromophore and exhibits many spectroscopic properties common to linear polyenes. Its absorption spectrum is characterized by a strong near-ultraviolet transition with vibronic structure, which is strongly affected by solvent polarizability. The fluorescence emission occurs at considerably lower energy than the absorption and the wavelength of the emission is nearly independent of the solvent. The fluorescence quantum yield and lifetime are strongly affected by temperature and solvent. These spectral features are interpreted in terms of an excited electronic-state order such that a weak transition occurs at longer wavelengths than the strongly allowed transition which dominates the absorption. The sensitivity of the fluorescence quantum yield an lifetime to environment is shown to be due primarily to variations in the nonradiative rate, although changes in the radiative rate constant are also observed and interpreted. The absorption spectrum (epsilon max greater than 65 000) is in the 300-320-nm range, a region relatively free of absorption due to intrinsic biological chromophores. Shifts of several nanometers are characteristic of different environments. These shifts are compared to similar effects observed for a series of diphenylpolyenes for which new data are given and are correlated using a simple but adequate theory of solvent shifts. The intrinsic (or radiative) fluorescence lifetime is near 100 ns in a wide variety of environments. This is much longer than the intrinsic lifetime calculated from the absorption spectrum and strongly supports the proposed excited-state order.

Neuronal control of locomotion in the lobster,Homarus americanus

Abstract: 1. Lobsters that are tethered in place on a treadmill (Fig. 3) walk against the direction of belt movement (Table 2). Forward and backward locomotion over the full range of step frequencies can be controlled by this method, even in the absence of visual input. The passive traction provided by a moving substrate is therefore an effective stimulus for walking and presumably operates in parallel with previously described optomotor pathways to provide positive feedback reinforcement of locomotory behavior. 2. The movements (Figs. 1, 6) and muscular anatomy (Fig. 2) of a lobster walking leg are described. On the basis of simultaneous extracellular recording from several leg muscles (Fig. 5), and motion picture analysis, the overall patterns of joint movement and muscular coordination underlying forward and backward walking are described (Figs. 5, 6, 7). 3. Some muscles that are synergic for forward walking are antagonistic for backward walking (Figs. 6, 7). Similarly movements that are synergic for lateral walking on the leading side are antagonistic for lateral walking on the trailing side (Fig. 6). 4. Quantitative analysis of leg movements (Fig. 9) and electromyograms (Fig. 10) have shown that the walking muscles can be subdivided into three different functional classes: return stroke muscles, which exhibit bursts of relatively constant duration irrespective of step frequency (Fig. 10A); power stroke muscles in which burst duration varies linearly with step frequency (Fig. 10B); and bifunctional muscles, which exhibit the discharge characteristics of either return or power stroke muscles, depending on the direction of walking (Fig. 10C). 5. Several lines of evidence (Table 3, Figs. 6, 7, 9, 10, 12) suggest that the limb elevator motoneurones (or their central antecedents) function as the central pacemaker of the walking system, and that other cyclic leg movements are appended to the basic elevation/depression cycle as appropriate to the direction of walking. Evidence is presented that proprioceptive inputs provided by passive traction are capable of controlling the direction of locomotion (Table 2), and determining the periodicity of stepping (Fig. 4), by altering the duration of powerstroke bursts (Figs. 9, 10, 15).

The role of the metacerebral giant neuron in the feeding behavior ofPleurobranchaea

Abstract: The metacerebral giant (MCG) neurons of the molluskPleurobranchaea have been analyzed using a wide range of methods (cobalt staining, histochemical, biophysical and electrophysiological) on several types of preparations (isolated nervous systems, semi-intact preparations, and behaving whole-animal preparations). The MCG is serotonergic. The bilaterally-symmetrical neurons have somata in the anterior brain. Each MCG neuron sends an axon out the ipsilateral mouth nerve of the brain and also into the ipsilateral cerebrobuccal connective which descends to the buccal ganglion. The descending axon sends one or more branches out most buccal nerves.

New hominoid primates from the Siwaliks of Pakistan and their bearing on hominoid evolution

Abstract: Siwalik deposits in the Punjab have yielded a rich collection of hominoidprimate remains. Together with other recent finds they indicate the need for some changes in hominoid classification.

On the bifurcation of maps of the interval

Abstract: In the last few years there has been considerable interest in the asymptotic behavior of maps of the interval into itself under iteration. Some of this interest has come from the theory of dynamical systems (where most authors have studied maps of the circle), and some of the interest has been generated by population biology. In population biology, maps of the unit interval have been used as models for the dynamics of populations with discrete generations. One of the questions of most interest in the theory has been the determination of the limit sets of points for a map f : I -* I. Here I=[0 , 1]. The limit set ofxs t is the set of limit points of the sequence {f~(x)}. The superscript denotes repeated composition. Of particular interest are periodic orbits: points x such that f~(x)= x for some i>0. Even greater interest focuses upon attracting periodic orbits: if

Movement and feeding activity of red sea urchins (Strongylocentrotus franciscanus) adjacent to a kelp forest

Abstract: Movement and feeding were studied in a population of red sea urchins, Strongylocentrotus franciscanus (Agassiz, 1863), found within and immediately seaward of a kelp forest offshore from Santa Cruz, California, USA. Mean sea urchin movements varied from 7.5 cm/day inside the kelp forest to over 50 cm/day at 15 and 100 m outside the kelp forest. The percentage of sea urchins feeding decreased from 66% inside the kelp forest to 16 and 15% at 15 and 100 m outside the kelp forest. These data indicate that movement by these sea urchins is a response to a low food supply.

Monitoring the marine environment through sedimentation

Abstract: The argument is advanced that the interception of particles settling within the water column provides a means of monitoring and understanding basic ocean processes. Geochemical and biological measurements on precisely dated bottom sediments and on preliminary recoveries from particle interceptor-traps provide supporting evidence.

Solar energy storage, production of hydrogen by 546-nm irradiation of a dinuclear rhodium(I) complex in acidic aqueous solution

Abstract: A logical avenue for exploratory research on (Rh/sub 2/(bridge)/sub 4/)/sup 2 +/ (bridge = 1,3-diisocyanopropane) involves its excited-state reactivity behavior, as a directly coupled dinuclear redox center might be able to channel charge-transfer excitation energy into redox-substrate chemical bond formation at rates that are competitive with back electron transfer. This goal has been achieved in one important case, namely, in the reduction of protons 40 hydrogen through 546-nm irradiation of (Rh/sub 2/(bridge)/sub 4/)/sup 2 +/ in aqueous HCl solution.

Immune Response in the Sea Urchin Lytechinus pictus

Abstract: The sea urchin shows an immune response to grafted tissue similar to that found in vertebrates. Unrelated animals rejected allografts in about 30 days. Acceptance of allografts was observed for tissue exchanged between some F2 and F3 inbred animals. The percentage of acceptances reflected the degree of inbreeding. Accelerated second set rejection was also found. These grafts were rejected in one-third of the time compared to first sets.

Metabolism of Oat Leaves during Senescence: V. Senescence in Light.

Abstract: A comparison has been made of the progress of senescence in the first leaf of 7-day-old oat plants (Avena sativa cv. Victory) in darkness and in white light. Light delays the senescence, and intensities not over 100 to 200 ft-c (1000-2000 lux) suffice for the maximum effect. In such intensities, chlorophyll loss and amino acid liberation still go on in detached leaves at one-third to one-half the rate observed in darkness; however, when the leaves are attached to the plant, the loss of chlorophyll in 5 days is barely detectable. Transfer of the leaves from 1 or 2 days in the low intensity light to darkness, or vice versa, shows no carryover of the effects of the preceding exposure, so that such treatment affords no evidence for the photoproduction of a stable substance, such as cytokinin, inhibiting senescence. Light causes a large increase in invertaselabile sugar and a smaller increase in glucose, and application of 100 to 300 mm glucose or sucrose in the dark maintains the chlorophyll, at least partially. Correspondingly, short exposure to high light intensity, which increased the sugar content, had a moderate effect in maintaining the chlorophyll. However, 3-(3,4-dichlorphenyl)-1,1-dimethylurea (DCMU) completely prevents the increases in sugars and yet does not prevent the effect of light on senescence, whether determined by chlorophyll loss or by protein hydrolysis. Light causes a 300% increase in the respiration of detached oat leaves, and kinetin lowers that only partly, but unlike the increased respiration associated with senescence in the dark, the increase in the light is fully sensitive to dinitrophenol, and therefore cannot be ascribed to respiratory uncoupling. The increased respiration in light is prevented by DCMU, parallel with the prevention of sugar formation. It is therefore ascribed to the accumulation of soluble sugars, acting as respirable substrate. Also, l-serine does not antagonize the light effect. For all of these reasons, it is concluded that the action of light is not mediated by photosynthetic sugar formation, nor by photoproduction of a cytokinin. Instead, we propose that light exerts its effect by photoproduction of ATP. The action of sugars is ascribed to the same mechanism but by way of respiratory ATP. This hypothesis unifies most of the observed phenomena of the senescence process in oat leaves, and helps to explain some of the divergent findings of earlier workers.

Organization of Invertebrate Motor Systems

Abstract: The sections in this article are: 1 Properties of Muscle 11 Anatomic Organization 12 Contraction Speed 13 Strength and Extent of Contraction 14 Thresholds for Excitation-Contraction Coupling 15 Correlations with Innervation 16 Dependence of Tension on Recent History 2 Motor Neurons and the Motor Unit 21 Motor Neuron Morphology 22 Correlations Between Motor Neuron Morphology and Function 23 Neuromuscular Transmission 24 Excitation-Contraction Coupling 25 Peripheral Motor Unit Organization 26 Matching of Central and Peripheral Properties 27 Ontogeny and Regeneration 3 Reflex Organization 31 Proprioceptive Reflexes 32 Exteroreceptive Reflexes 33 Righting Reflexes 34 Optomotor Reflexes 35 Control of Reflex Excitability 4 Central Organization of Motor Systems 41 Structure of Motor Programs 42 Storage of Motor Programs 43 Release of Motor Programs by Command Elements 44 Central Versus Peripheral Control of Motor Output 45 Development of Pattern-Generating Networks 46 Complex Behavioral Phenomena 5 Conclusion

Isotopic anomalies and proton irradiation in the early solar system

Abstract: Nuclear cross sections relevant to the various isotopic-abundance anomalies found in solar-system objects are evaluated in an attempt to set constraints on the hypothesized mechanism of irradiation of forming planetesimals by energetic protons from the young sun. A power-law proton spectrum is adopted, attention is restricted to proton energies less than about 20 MeV, and average cross sections are calculated for several reactions that might be expected to lead to the observed anomalies. The following specific anomalies are examined in detail: Al-26, Na-22, Xe-126, I-129, Kr-80, V-50, Nb-92, La-138, Ta-180, Hg-196, K-40, Ar-36, O-17, O-18, N-15, C-13, Li, Be, and B. It is suggested that the picture of presolar-grain carriers accounts for the facts more naturally than do irradiation models.

Krameria, free fatty acids and oil-collecting bees

Abstract: VOGEL'S report1,2 of the production of glycerides rather than nectar as rewards gathered by bees described an association involving several genera of insects and numerous plant families. We report here that members of the Krameriaceae produce floral lips more unusual than those described by Vogel2. Our data also provide evidence that the oils of Krameria are collected by bees of only one genus, Centris (Anthophoridae), and used, mixed with pollen, as larval food.

Asymptotic freedom and the baryon-quark phase transition

Abstract: We have calculated the ground-state properties of a quark gas to second order in the quark-gluon coupling constant. Asymptotic freedom has been taken into account by using the renormalized coupling constant of Politzer and Gross and Wilczek. We find that this asymptotically free perturbation theory leads to an equation of state for a quark gas which for pressure P > 0 is very similar to the equation of state obtained from the MIT bag model of hadrons. In particular, we can identify a ''bag pressure'' term in the perturbation theory expression for the pressure as a function of density. We obtain estimates for the baryon-quark transition pressure by comparing the perturbation theory results for the Gibb's energy per baryon of baryonic matter. Our calculations show that the baryon-quark transition takes place at densities on the order of 10--20 times that in ordinary nuclei. These transition densities are higher than the maximum central density calculated for a neutron star.

Hypnosis from the standpoint of a contextualist

Abstract: We set out to formulate a theory that makes counterexpectational conduct expectational. Our contextualist position has led us to the dramaturgical perspective. This perspective guided our examination of the hypnotic performance, and we noted that both the hypnotist and the subject are actors, both enmeshed in a dramatic plot, both striving to enhance their credibility. The dramatistic concepts of actor and spectator helped us make sense of the contradictory self-reports in Hilgard's analgesia studies. We underscore the proposition (long overlooked) that the counterfactual statements in the hypnotist's induction are cues to the subject that a dramatistic plot is in the making. The subject may respond to the cues as an invitation to join in the miniature drama. If he accepts the invitation, he will employ whatever skills he possesses in order to enhance his credibility in enacting the role of hypnotized person. This proposition emphasizes the need for analyzing the implied social communications contained in any interaction.

Lipid Composition of Organelles from Germinating Castor Bean Endosperm

Abstract: Glyoxysome, endoplasmic reticulum, mitochondria, and proplastid fractions were isolated from endosperm of castor beans ( Ricinus communis ) germinated for 5 days at 30 C. Samples from sucrose density gradients were diluted with 0.15 m KCI and the membranes pelleted. Lipid extracts of these membranes were analyzed for phosphoglyceride, acyl lipid, and sterol content. The endoplasmic reticulum contains 1.24 μmol of phosphoglyceride per mg of protein; the mitochondria, 0.65 μmol/mg; and the glyoxysome membranes, 0.55 μmol/mg. Phosphatidyl choline and phosphatidyl ethanolamine are the most abundant lipids in all membranes studied, accounting for 70% or more of the lipid phosphorus and 50% or more of the fatty acid. Glyoxysome membranes and endoplasmic reticulum also contain phosphatidyl inositol (respectively, 9 and 17% of the lipid phosphorus) and free fatty acids (13% of the total fatty acid in each). Compared with other organelles, mitochondrial membranes have more phosphatidyl ethanolamine relative to phosphatidyl choline and are characterized by the presence of cardiolipin, in which 80% of the fatty acid is linoleate. The relative amounts of linoleate, palmitate, oleate, stearate, and linolenate in each of the phosphotoglycerides are constant regardless of the membrane source. Stimasgasterol and β-sitosterol are present in the membranes (1-9 nmol each/mg protein). The data provide further evidence that glyoxysome membranes are derived from the endoplasmic reticulum but at the same time indicate some differentiation.

A measure of individual differences in sex stereotyping and sex discrimination: The Macho scale.

Abstract: A personality measure of individual differences in sex-role stereotyping and sex discrimination was developed. The “Macho” scale fulfills satisfactory psychometric criteria of internal consistency ...

The Command Neuron

Abstract: Of the many important concepts that have stemmed from the prolific research of Professor C. A. G. Wiersma, perhaps the one that has had the greatest impact on comparative neurobiology is that of the “command” neuron. The term has a long history of application in the invertebrates (for recent reviews, see Bowerman and Larimer, 1976a; Davis, 1976; Kennedy and Davis, 1977) and has recently found its way into the mammalian literature (Grillner, 1975). As evidenced at this symposium, however, the concept has also stirred considerable debate. Given the importance of the topic and the incompleteness of existing data on such neurons, this debate is both inevitable and desirable. As I hope to show in this chapter, such debate can help to clarify our thinking on the subject of the command neuron and can also illuminate fruitful areas for future research.